Typically, modern semi-automatic and automatic weapons include a gas tube and/or a gas cylinder part that is used in cycling the firearm (e.g., ejecting a fired cartridge and inserting a new cartridge). For instance, DE 1 453 904 A, U.S. Pat. No. 1,350,961, DE 103 18 828 A1, and DE 29 32 710 A1, describe gas cylinder parts for use with firearms. The gas cylinder is typically positioned above the barrel so not to interfere with the magazine (e.g., the mechanism for supplying cartridges to the weapon). The position of the gas cylinder, which is just below a shooter's line of sight, allows for a recoil of the firearm to proceed in the direction of the shooter's shoulder and not above it, which has been the general rule for rifles (e.g., military and/or hunting rifles) from the beginning of the twentieth century.
The gas cylinder of automatic rifles, such as, for example, the AK 74, is not mounted on the muzzle. However, the sight base is coupled to the muzzle and the shooter typically wants to retain a line of sight as long as possible. It is difficult to mount the sight base to the muzzle because the sight base must not wobble and must absorb a heavy blow from, for example, firing and/or cycling the weapon, without displacing or bending. The gas cylinder is securely coupled to the barrel, but has certain tolerances as long as the bores in the barrel and in the gas cylinder meet, which is why one of the bores in the barrel or in the gas cylinder is typically larger than the other.
Additionally, automatic rifles include fixtures for coupling a hand guard, and/or grenade launcher to the rifle. The hand guard has to be parallel to the line of sight if fixtures for accessory devices are to be coupled to the hand guard, such as, for example, a Picatinny rail.
In some instances, if additional optical and/or electronic sighting mechanism(s) are used, the line of sight of the optical and/or electronic sighting mechanism(s) may not be anatomically designed for the rifleman, and, therefore, may not be used optimally. Collapsible sights are known that free the line of sight by tilting the sight, such as, for example, Swiss assault rifle 57, however, these sights have to be tilted upwards every time prior to using the rifle, and, thus, additional time is needed if the shooter does not want to take an unaimed shot.